MOSFETs with short channels are advantageous in that they use less area on a chip thereby allowing more functionality on the chip, have lower on resistance (Ron), and have faster switching characteristics compared to conventional MOSFETs. However, shortening the channel generally gives rise to disadvantages generally known as “short channel effects.” Such effects include hot carrier injection (HCl) into the gate oxide and into the device substrate which affect the reliability of the device and can degrade Ron of the device. Another short channel effect is the decrease in the punch through voltage of the device, therefore, the decrease in the drain to source breakdown voltage (BVdss) of the device. The effect is particularly problematic for MOSFETs which are used in medium voltage and high voltage applications, especially if such MOSFETs are on the same die as low voltage circuits.
Therefore, short channel LV, MV, and HV CMOS devices which reduce these short channel effects compared to prior art short channel MOSFETs is desirable.
Further, short channel MV and HV CMOS devices which can be placed on the same die as LV devices is also desirable.